Suborder TEREBRATULIDINA

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Introduction

The Terebratulidina are diagnosed by having a short loop and the medium septum absent. Two superfamilies are included, the Terebratuloidea and Cancellothyroidea, both of which are distributed worldwide. The superfamilies have been studied in detail by Cooper (respectively 1983 and 1973). They are distinguished on details of loop form and on the presence or absence of hinge plates. Hinge plates are used for the attachment of dorsal pedicle muscles. In the absence of plates, the muscles are attached to the floor of the dorsal valve. In terebratuloids the hinge plate is present and the crural processes of the loop are discrete. Cancellothyroids lack a medium septum and hinge plates and the crural processes of the loop unite to form a ring.

There are two living terebratuloid families, the Terebratulidae and the Dyscoliidae. Only the cosmopolitan Terebratulidae occur in Australia.

Cooper (1973) included three families when he established the superfamily Cancellothyroidea. They are distinguished on the basis of crural processes discrete (Chlidinophoridae) or united to form a ring (Cancellothyroididae, Cnismatocentridae), and presence (Cancellothyridiodea, Chlidinophoridae) or absence of costae (Cnismatocentridae). Cancellothyroideans are distributed worldwide at depths ranging from the intertidal to 4205 m. All are pediculate and, as in terebratuloideans, the pedicle is used for bondage to hard substrata or for tethering in soft sediments.

Occurrence: Lower Devonian to Recent.

General References

Cooper, G.A. 1973. Vema's Brachiopoda (Recent). Smithsonian Contributions to Paleobiology 17: 20

Cooper, G.A. 1983. The Terebratulacea (Brachiopoda), Triassic to Recent: a study of the Brachidia (loops). Smithsonian Contributions to Paleobiology 50: 445

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